If your Rails app is content-heavy, consider organizing it in a tree menu structure. Here I show how to add top-level tabs, nested links in a side bar, and breadcrumbs to go up the hierarchy.
(10 minutes)

If you have a page containing a dynamic list of records, consider providing an RSS or Atom feed for it. It is quite easy to do with XML Builder and the atom_feed helper method as shown in this episode.
(8 minutes)